We report resonant Raman spectroscopy of neutral excitons ${\mathrm{X}}^0$ and intravalley trions ${\mathrm{X}}^{-}$ in hBN-encapsulated ${\mathrm{MoS}}_2$ monolayer embedded in a nanobeam cavity. By temperature tuning the detuning between Raman modes of ${\mathrm{MoS}}_2$ lattice phonons and ${\mathrm{X}}^0/{\mathrm{X}}^{-}$ emission peaks, we probe the mutual coupling of excitons, lattice phonons and cavity vibrational phonons. We observe an enhancement of ${\mathrm{X}}^0$-induced Raman scattering and a suppression for ${\mathrm{X}}^{-}$-induced, and explain our findings as arising from the tripartite exciton-phonon-phonon coupling. The cavity vibrational phonons provide intermediate replica states of ${\mathrm{X}}^0$ for resonance conditions in the scattering of lattice phonons, thus enhancing the Raman intensity. In contrast, the tripartite coupling involving ${\mathrm{X}}^{-}$ is found to be much weaker, an observation explained by the geometry-dependent polarity of the electron and hole deformation potentials. Our results indicate that phononic hybridization between lattice and nanomechanical modes plays a key role in the excitonic photophysics and light-matter interaction in 2D-material nanophotonic systems.

• Received 3 June 2022
• Revised 23 January 2023
• Accepted 28 February 2023

DOI:https://doi.org/10.1103/PhysRevLett.130.126901